(Bloomberg) – The latest U.S. government report on climate change illustrates how expensive the phenomenon can be: It estimates that more frequent flooding, more violent hurricanes and more intense wildfires, among other things, have cost the country $1.1 trillion since 1980.

What's particularly striking, though, is how much the report and others like it are still missing.

For two decades, researchers have been working hard to figure out the potential monetary consequences of climate change. They typically look at things that are relatively easy to measure, such as flood damage from more intense rainfall, real estate losses along coastlines and reduced economic growth. Yet as a new review of the most widely used models points out, they also leave out some pretty big things, such as greater damage from wildfires, worsening water scarcity and the potential for shifting climate patterns to trigger social and political instability by disrupting agriculture and ecology.

Estimating such effects is inherently difficult, but ignoring them is worse. Serious consequences are already evident, in the recent string of U.S. hurricanes and rampant wildfires in California and elsewhere. In West Africa, persistent changes in the amount and timing of rainfall have caused a mass migration, primarily of young men, to Europe and elsewhere. The uprising in Syria came just after a crippling four-year drought caused widespread food shortages. In Europe, a surge of migrants from Syria and elsewhere has played a significant role in the rise of populist parties and a spreading backlash against democracy.

In other words, the U.S. Defense Department was prescient two years ago when it concluded that “climate change is an urgent and growing threat to our national security, contributing to increased natural disasters, refugee flows, and conflicts over basic resources such as food and water.” Although climate change hasn't necessarily caused such ills, it has certainly exacerbated them.

The British scientist and journalist Nafeez Mosaddeq Ahmed has made one of the few attempts to forge a more integrated picture of how climate change, by altering the biosphere, is likely to affect geopolitics. As he notes, the traditional approach is to explain sociopolitical instability by looking at things like national rivalries and competition, political corruption or ideological or religious extremism. We generally ignore or undervalue how deeper biophysical factors, by disrupting the economy or putting increased stress on fragile relationships, can trigger or amplify instability. [more]